1. Field of the Invention
The present invention relates to the separation of amino acids from a mixture of at least two amino acids, and, more especially, to the production of amino acids from protein hydrolysates.
2. Description of the Prior Art
A number of different techniques are known to this art for the production of amino acids, the most common of which entail chemical or biochemical syntheses. These techniques generally provide a single amino acid in solution in the medium of preparation. Extraction of such single amino acid and the purification thereof are typically feasible on an industrial scale.
At the present time, however, certain of the amino acids can be produced industrially only with difficulty, and only by chemical methods or fermentation.
All of the amino acids exist as units of peptides and proteins and are components of all life forms, whether vegetable or animal. Attempts have therefore been made to hydrolyze such proteins to extract therefrom the different amino acids. In proteinaceous materials, the amino acids are intermixed in large numbers, on the order of approximately 20.
Various methods have been attempted to separate these amino acids. It will be appreciated that all of the amino acids have physico-chemical properties which differ rather slightly and that in living matter they are all present together, frequently without a truly major component, which further exasperates the difficulty of their separation.
Among the separation techniques proposed in the literature, the following have been reported: precipitation, but here the efficiency of the separation is mediocre and the need to recover the precipitating reagent complicates the process; ion exchange processes which are difficult to carry out in view of the large size of the columns, the strong dilution of the solution and sequential mode of operation of the columns.
It too is known, from U.S. Pat. No. 2,894,954, to separate the amino acids selectively from acid solutions of amino acids, using an aliphatic alcohol solution, but the extraction capacity of the solvent remains low and, while this disadvantage has been partially overcome by the addition of hexylamine, the selectivity remains too weak.
None of the processes of the prior art enable the cost-effective separation of individual natural amino acids from mixtures of amino acids, notably the most commercially attractive of such amino acids, specifically arginine, phenylalanine, leucine, isoleucine, valine and histidine.